edr derives a sample of a respiratory
signal for each QRS complex in the input ECG, by measuring the mean electrical
axis (in two-channel mode) or the projection of that axis onto the lead
axis (in single-channel mode). See the references below for details of the
algorithm.

edr reads the signal and annotation files specified by record
and annotator, and writes another annotation file, which is a copy of the
input annotation file except that the num field of each beat annotation
is replaced by an EDR sample.

If the beat annotations are not located at
the QRS peaks, it will be necessary to set the window limits (the offsets
relative to the annotations between which the raw measurements for the
EDR are taken), using the -d option. By default, edr behaves as if the option
-d -0.04 0.04 has been given (in other words, measurements are taken over an
80 ms window beginning 40 ms (.04 seconds) before the annotation, and ending
40 ms after the annotation); this default is reasonable if the QRS annotations
have been placed on or near the QRS peaks or centroids. If edr is supplied
with annotations generated by sqrs, or another method that places the annotations
near the PQ junction (the beginning of the QRS complex), the option -d 0
0.08 is recommended.

For ECGs sampled at relatively low rates (e.g., 100-128
Hz, as is common for many long-term ECG recordings), it may be advantageous
to base the EDR on the T-wave rather than the QRS complex, by choosing a
window such as -d -0.08 0.28 or -d -0.12 0.32 (for annotations placed at the QRS
peaks or PQ junctions respectively), since this permits an axis estimation
based on a larger number of samples. Note that the use of a negative value
for dt1, as in these examples, allows the beginning of the EDR measurement
window to be placed after the QRS annotation.

Analyze only the signals named in the signal-list (one
or more input signal numbers, separated by spaces; default: analyze signals
0 and 1). If the signal-list contains more than two signals, only the first
two are analyzed.

This command creates an annotation file named edr.100, containing a copy
of the reference (atr) annotation file for the first five minutes of record
100, with EDR measurements for each annotated beat in the num fields of
the output annotation file.